Method and system for setting reference signal in wireless communication system

ABSTRACT

A method and a system of setting up a reference signal in a radio communication system. The radio communication system includes a serving cell and a neighboring cell, and a mobile terminal of the serving cell uses the same temporal frequency resource so as to receive a serving resource block from the serving cell and receive an interference resource block from the neighboring cell. The method according to the present disclosure includes a step of setting up a user-specific reference signal in the interference resource block and a step in which puncturing is performed at same temporal frequency position as the temporal frequency position at which the user-specific reference signal is set up on the interference resource block of the serving resource block so as to prevent any signal from being transmitted at the punctured temporal frequency position. When the method and the system provided in the present disclosure are used and the interference power between cells is thereby measured, it is possible to effectively reduce feedback overhead in a coordinated beamforming.

TECHNICAL FIELD

The present disclosure relates to a multi-antenna signal transmissiontechnology in a communication field.

BACKGROUND ART

In today's cellular network radio communication system (for example, LTEand WiMAX), user equipment (UE) receives not only a signal of a servingbase station but also interference between neighboring base stations(i.e., inter-cell interference). Inter-cell interference becomescomparatively stronger and becomes a major factor to limit systemthroughput when the user is at the cell edge.

Multiple base station cooperation is a type of technology foreffectively reducing interference between cells. Coordinated beamformingis a type of method that can realize multiple base station cooperation.When a plurality of antennas are placed at a base station, the antennadirectivity can be changed according to a precoding vector of an antennaarray, a signal of a serving cell can be increased, and at the sametime, the interference from the neighboring cells can be reduced.

FIG. 1 is a model of a coordinated beamforming between eachcommunication cell in a communication system. As shown in FIG. 1, thesystem includes three (but not limited to three) base stations (cells)eNB 1, eNB 2, and eNB 3 in which, base station eNB 1 is the serving basestation of the user equipment (UE) located at the border of the threecells. UE receives a signal from its own serving base station eNB 1 butat the same time receives interference from the neighboring cells (basestations eNB 2 and eNB 3). User equipment UE needs to measure theserving cell channels and the neighboring cell channels and then give aperiodic feedback to serving base station eNB 1 about channelinformation on these channels. As a result, serving base station eNB 1designs a precoding vector of the beam forming and strengthens thesignal of serving cell eNB 1, and notifies the channel information onthe corresponding channel through an inter-base station communication tothe base station of the corresponding cell; and reduces the interferenceto the serving cell eNB 1 by adjusting the precoding vector of its ownself beam forming in these base stations.

The channel information herein may be PMI (Precoding Matrix Index) ofeach channel or CSI (Channel Status Information), and the like.

FIG. 2 is a schematic diagram illustrating a channel information reportto base station eNB 1 of the serving cell of user equipment UE. As shownin FIG. 2, along with the passage of time, user equipment UE reports theall channel information of the three cells, such as precoding matrixindex PMI-1 of serving cell eNB 1, and precoding matrix index PMI-2 andprecoding matrix index PMI-3 of two neighboring cells eNB 2 and eNB 3,to serving base station eNB 1 of the serving cell once per cycle T.

In the above coordinated beamforming, user equipment UE needs to givenot only a feedback on the channel information of serving cell eNB 1 butalso a feedback on the channel information of the neighboring cells, andthus, as compared to the conventional system without the cooperativetransmission between cells, the coordinated beamforming requires alarger feedback overhead. Therefore, a challenge of the coordinatedbeamforming is to effectively reduce feedback overhead.

SUMMARY OF INVENTION

According to one aspect of the present disclosure, there is provided amethod of setting up a reference signal in a radio communication system.The radio communication system includes a serving cell and a neighboringcell. A mobile terminal of the serving cell uses the same temporalfrequency resource so as to receive a serving resource block from theserving cell and receive an interference resource block from theneighboring cell. The method according to the present disclosureincludes a step of setting up a user-specific reference signal in theinterference resource block, and a step in which puncturing is performedat the same temporal frequency position as the temporal frequencyposition at which the user-specific reference signal is set up on theinterference resource block in the serving resource block so as toprevent any signal from being transmitted at the punctured temporalfrequency position.

According to another aspect of the present disclosure, there is provideda radio communication system. The radio communication system includes aserving cell and a neighboring cell. A mobile terminal of the servingcell uses the same temporal frequency resource so as to receive aserving resource block from the serving cell and receive an interferenceresource block from the neighboring cell. The radio communication systemincludes an set up section that set ups a user-specific reference signalin the interference resource block, and a puncturing section thatperforms puncturing at the same temporal frequency position as thetemporal frequency position at which the user-specific reference signalis set up on the interference resource block in the serving resourceblock so as to prevent any signal from being transmitted at thepunctured temporal frequency position.

When a method and a system of setting up a reference signal provided inthe present disclosure is used, and at the same time, when aninterference power between cells is measured by using the same, it ispossible to effectively reduce feedback overhead in a coordinatedbeamforming.

BRIEF DESCRIPTION OF DRAWINGS

These aspects and/or other aspects and advantages of the presentdisclosure become clearer and easier to understand from the detaileddescription given below which is a combination of the drawings andembodiments of the present disclosure. In the drawings,

FIG. 1 shows a model of a coordinated beamforming between eachcommunication cell in a communication system;

FIG. 2 is a schematic diagram illustrating a channel information reportto a base station of a serving cell of a user equipment;

FIG. 3( a) and FIG. 3( b) are schematic diagrams illustrating inter-cellinterference;

FIG. 4( a) and FIG. 4( b) are schematic diagrams illustrating anadaptive feedback method according to an embodiment of the presentdisclosure;

FIG. 5( a) and FIG. 5( b) are diagrams illustrating an set up auser-specific reference signal on an interference resource blockaccording to the embodiment of the present disclosure;

FIG. 6( a) and FIG. 6( b) are diagrams illustrating an set up of auser-specific reference signal, as a demodulation reference signal,according to the embodiment of the present disclosure;

FIG. 7( a) and FIG. 7( b) are diagrams illustrating an set up of auser-specific reference signal, as a demodulation reference signal,according to another embodiment of the present disclosure;

FIG. 8( a), FIG. 8( b), and FIG. 8( c) are other schematic diagramsillustrating inter-cell interference;

FIG. 9( a) and FIG. 9( b) are diagrams illustrating an set up of auser-specific reference signal, as a demodulation reference signal,according to still another embodiment;

FIG. 10 is a diagram illustrating a power sensing reference signalaccording to still another embodiment of the present disclosure;

FIG. 11( a) and FIG. 11( b) are diagrams illustrating an set up of thepower sensing reference signal to a data signal position according tothe embodiment of the present disclosure;

FIG. 12( a) and FIG. 12( b) are diagrams illustrating an set up of thepower sensing reference signal to a demodulation reference signalposition according to the embodiment of the present disclosure;

FIG. 13( a) and FIG. 13( b) are another diagrams illustrating an set upof the power sensing reference signal to the demodulation referencesignal position according to the embodiment of the present disclosure;

FIG. 14 is a diagram illustrating an set up of the power sensingreference signal according to another embodiment of the presentdisclosure;

FIG. 15 is a diagram illustrating an set up of the power sensingreference signal when interference arrives from a plurality of terminalsof neighboring cells;

FIG. 16 is a diagram illustrating another example of an set up of thepower sensing reference signal when the interference arrives from theplurality of terminals of the neighboring cells;

FIG. 17 is a diagram illustrating the generation of an interferenceresource block due to the existence of a plurality of mobile terminalsin the neighboring cells;

FIG. 18 is a diagram illustrating a basic arrangement of a radiocommunication system to realize the embodiment of the presentdisclosure; and

FIG. 19 is a flow chart illustrating a method of realizing theembodiment of the present disclosure.

DESCRIPTION OF EMBODIMENTS

Specific embodiments of the present disclosure are described in detailin combination with the drawings. The detailed descriptions of some ofthe relating conventional technologies are not provided if the detaileddescriptions thereof may make the essential points of the presentdisclosure ambiguous. Elements or means that execute the same functionsare assigned with same signs in each embodiment.

The present disclosure proposes the measurement of an interference powerbetween cells according to a method of setting up a user-specificreference signal in a downlink of a radio communication system. In aspecific method, a neighboring cell (interference cell) set ups auser-specific reference signal on a resource block (interferenceresource block) to be transmitted, and a serving cell (interfered cell)performs puncturing at the same temporal frequency position at thetemporal frequency positions at which the user-specific reference signalexist, on a resource block (serving resource block) transmitted to itsown user equipment (for example, a mobile terminal). This disclosurefurther proposes a method in which a “Power sensing reference signal” isset up and the power sensing reference signal is used as theuser-specific reference signal. Thus, even if an interfered user is notaware of the number of interference signal layers, it is possible toaccurately sense a total interference power. The beampattern of thispower sensing reference signal may be equivalent or almost equivalent toa sum of beampattern of the interference signal in each layer. Whenthere is interference from signals of a plurality of users, this powersensing reference signal can be used for measurement of the interferencepower of a plurality of users.

FIG. 3( a) and FIG. 3( b) are schematic diagrams illustrating inter-cellinterference. As shown in FIG. 3( a), when cell base station eNB 1communicates with mobile terminal UE 1, the power of an antenna beam isfocused mainly in the direction of UE 1, and similarly, when cell basestation eNB 2 communicates with mobile terminal UE 2, the power of anantenna beam is focused mainly in the direction of UE 2. However, whenUE 1 and UE 2 receive signals from their own respective serving basestations eNB 1 and eNB 2, these UEs receive interference (illustratedwith a dotted line in FIG. 3( a)) from the neighboring cells eNB 1 andeNB 2. However, in some cases, as shown in FIG. 3( b), the antenna beamdirection of cell base station eNB 2 is remote from mobile terminal UE1, and as such, when UE 1 communicates with serving base station eNB 1,the interference received from neighboring base station eNB 2 becomescomparatively small, as a result of which the interference for thecommunication also is comparatively small. On the other hand, in asituation depicted in FIG. 3( a), the antenna beam direction of cellbase station eNB 2 is more closer to mobile terminal UE 1, and becauseof this, when UE 1 communicates with serving base station eNB 1, theinterference received from neighboring base station eNB 2 becomescomparatively large, as a result of which the interference for thecommunication may also become comparatively large.

The present disclosure proposes in such a situation a solution that canreduce feedback overhead, i.e., proposes a solution in which, a mobileterminal gives a feedback on channel information of neighboring cells tothe serving base station only when there is definitely inter-cellinterference and considers that it is not necessary to give the feedbackon the channel information of this neighboring cells when there is nointer-cell interference (signal). Such a feedback method can be calledas an adaptive feedback method rather than a periodic feedback method.

FIG. 4( a) and FIG. 4( b) are schematic diagrams illustrating theadaptive feedback method according to the embodiment of the presentdisclosure. A vertical block in FIG. 4( b) represents interferencepower, that mobile terminal UE 1 receives, from the neighboring cell eNB2. If the value of interference power from the neighboring cells eNB 2,measured in UE 1, exceeds a predetermined threshold value (the thresholdvalue can be set up by a person skilled in the art according to theactual demand of the system), then UE 1 reports the interference powerto serving cell eNB 1, and if the value of the received interferencepower does not exceed the predetermined threshold value, then mobileterminal UE 1 does not report the interference power to serving basestation eNB 1. That is, it is necessary to determine whether to reportaccording to the size of the interference power of the neighboringcells.

In the above adaptive feedback method, mobile terminal UE 1 is requiredto effectively measure the interference power of the neighboring cells;however, the conventional inter-cell channel estimation methods are allbased on CSI-RS (CSI reference signal). CSI-RS is a cell-specificsignal, and this means that the CSI-RS can be transmitted normally evenwhen there is no interference between the cells (i.e., even when thereal interference signal is not transmitted). Therefore, theinterference power of the neighboring cells cannot be exactly reflectedin the measurements based on CSI-RS.

The embodiments of the present disclosure propose a solution thatmeasures the interference power of the neighboring cells. This solutionis performed based not on a cell-specific reference signal but on auser-specific reference signal. In this way, it is possible toeffectively understand the interference power of the neighboring cells.In this case, the user-specific reference signal is a precoded referencesignal transmitted together with data transmitted to a mobile terminal,and includes precoding vector information of an antenna of the cell.Specifically, when a communication base station of an interfered cell,for example, eNB 1, performs puncturing on data on a temporal frequencyposition (specific time and frequency) corresponding to theuser-specific reference signal of the neighboring cells eNB 2 and/or eNB3, in other words, does not transmit any data on the temporal frequencyposition, the reception power obtained by measuring on this temporalfrequency position, is the interference power of the neighboring cells.

The embodiments of the present disclosure are specifically described incombination with the drawings below.

FIG. 5( a) and FIG. 5( b) are diagrams illustrating the user-specificreference signal set up on the interference resource block, according tothe embodiment of the present disclosure. Under the environment shown inFIG. 3( a) and FIG. 3( b), mobile terminal UE 1 can receive the servingsignal from its serving base station eNB 1, and at the same time,receive the interference signal from base station eNB 2 (interferencesource) of the neighboring cells. FIG. 5( a) represents resource block(referred to as “serving resource block” below) RB 1 of a signal thatmobile terminal UE 1 receives from serving cell eNB 1, where ahorizontal axis denotes time t, a vertical axis denotes frequency, andrespective squares each denote a resource element. All the informationsignal resources that mobile terminal UE 1 receives from serving basestation eNB 1 are configured by a plurality of serving resource blocksRB 1 that are continuous in time and frequency. Each serving resourceblock RB 1 is an information signal transmitted over one time range (forexample, from time t1 to time t2) and one frequency range (for example,from frequency f1 to frequency f2). The resource elements in the firstthree rows of serving resource block RB 1 are control zones that areresponsible for the transmission of control data, and the resourceelements represented by a slanting line specifically represent Rel-8 RS(Rel-8 reference signal) of the LTE system. A resource element shownwithout any color is used to transmit a data signal. A dark coloredresource element is a cell-specific CSI-RS signal. The quantity ofCSI-RS signals does not limit the present disclosure, and any quantityof CSI-RS signals may be set up according to a system requirement.

FIG. 5( b) shows resource block (referred to as “interference resourceblock” below) RB 2 of the interference signal that mobile terminal UE 1receives from neighboring cells eNB 2. Similarly, the horizontal axis ofinterference resource block RB 2 denotes time t, a vertical axis denotesfrequency, and respective squares denote a resource element. Theresources of all the interference signals that mobile terminal UE 1receives from base station eNB 2 of the neighboring cells are configuredby a plurality of interference resource blocks RB 2 continuing in timeand frequency. Each interference resource block RB 2 is a signaltransmitted over one time range (for example, from time t1 to time t2)and one frequency range (for example, from frequency f1 to frequencyf2). The resource elements in the first three rows of interferenceresource block RB 2 are control zones that are responsible for thetransmission of the control data, and the resource element representedby a slanting line can specifically show Rel-8 RS (Rel-8 referencesignal) of the LTE system. A resource element shown without any color isused to transmit a data signal. A dark colored resource element is acell-specific CSI-RS signal. The quantity of CSI-RS signals does notlimit this disclosure and any quantity of CSI-RS signals may be set upaccording to the system requirement.

That is, serving resource block RB 1 and interference resource block RB2 are formed with a plurality of resource elements, respectively, andeach resource element occupies a different temporal frequency position(range of a specific time and frequency) and is used in the transmissionof a control signal, a channel status information reference signal,and/or a data signal. Since serving resource block RB 1 and interferenceresource block RB 2 are located on the same temporal frequency resource,these can be considered as overlapping.

According to the embodiment of the present disclosure, in a systemenvironment shown in FIG. 3( a) and FIG. 3( b), the radio communicationsystem includes serving cell (base station) eNB 1 and neighboring cell(base station) eNB 2, and when mobile terminal UE 1 of serving cell eNB1 uses the same temporal frequency resource, i.e., receives servingresource block RB 1 from serving cell eNB 1 as well as receivesinterference resource block RB 2 from neighboring cell eNB 2 within thesame time and frequency range, each cell eNB 1 and/or eNB 2 in the radiocommunication system set ups the reference signal in the downlinktransmitting to the corresponding mobile terminal (for example, UE 1and/or UE 2) as follows: neighboring cell eNB 2 set ups a user-specificreference signal in interference resource block RB 2 and serving celleNB 1 performs puncturing at the same temporal frequency position as thetemporal frequency position at which the user-specific reference signalis set up so as to prevent any signal from being transmitted at thepunctured temporal frequency position on the interference resource blockRB 2, in the serving resource block RB 1.

Specifically, it is possible to include one or a plurality ofuser-specific reference signals (only one signal is shown) ininterference resource block RB 2 shown in FIG. 5( b), and in this case,the signal is represented by an alphabet U. This user-specific referencesignal U, which undergoes the precoding of base station eNB 2 of theneighboring cell, is transmitted together with interference resourceblock RB 2, and includes precoding vector information by which the basestation eNB 2 of the neighboring cell communicates with the mobileterminal UE 2. In such a situation, serving base station eNB 1 of mobileterminal UE 1 can obtain a position in interference resource block RB 2of the user-specific reference signal U by cooperating (according to amethod well known by a person skilled in the art) with base station eNB2 of the neighboring cell, and performs puncturing at the same temporalfrequency position in the serving resource block RB 1 transmitted fromthe eNB 1 itself, as shown in the resource element (represented by U1)shown with a shaded line in serving resource block RB 1 in FIG. 5( a).That is, any signal is prevented from being transmitted in resourceelement U1 of serving resource block RB 1.

In this way, mobile terminal UE 1 can measure the power of theuser-specific reference signal at the punctured temporal frequencyposition, as the interference power that is received from neighboringcell eNB 2. Specifically, when mobile terminal UE 1 receives servingresource block RB 1 from serving base station eNB 1 and receivesinterference resource block RB 2 from base station eNB 2 of theneighboring cell with the same temporal frequency resource (within therange of the same time and frequency), the mobile terminal UE 1 canmeasure the total power of the signal at the positions (same temporalfrequency position) of the U and U1. Since resource element U1 does nottransmit any signal, the total power of the measured signal is power ofthe signal transmitted in U and can indicate the interference power fromneighboring cell eNB 2. This allows mobile terminal UE 1 to obtain theinterference power from neighboring cell eNB 2. Also, if theinterference power from the measured neighboring cell eNB 2 exceeds apredetermined threshold value, mobile terminal UE 1 reports theinterference power to serving cell eNB 1.

FIG. 6( a) and FIG. 6( b) are diagrams showing set up of theuser-specific reference signal, as a demodulation reference signal,according to the embodiment of the present disclosure. For example, inthe LTA-A radio communication system, a demodulation reference signal(DM-RS) is further included in the resource block transmitted by thecell base station, and this demodulation reference signal itself is auser-specific reference signal. That is, the demodulation referencesignal is a reference signal that has undergone precoding, transmittedalong with data that serving base station eNB 1 and/or eNB 2 transmitsto mobile terminal UE 1 and/or UE 2, includes precoding vectorinformation of the antenna of the transmission cell, and is a referencesignal by which mobile terminal UE 1 and/or UE 2 demodulates the datatransmitted by serving base station eNB 1 and/or eNB 2. Therefore, inFIG. 6( a) and FIG. 6( b), the demodulation reference signal is anactual example of the user-specific reference signals, i.e., it ispossible to set up the user-specific reference signal as thedemodulation reference signal in the interference resource block.

FIG. 6( a) and FIG. 6( b) are basically the same as FIG. 5( a) and FIG.5( b), so the same parts in FIG. 6( a) and FIG. 6( b) as those in FIG.5( a) and FIG. 5( b) are not described again; however, the demodulationreference signals are again shown in the serving resource block RB 1′ ofFIG. 6( a) and interference resource block RB 2′ in FIG. 6( b),respectively, and are shown by resource elements represented by ahorizontal line. In this case, the four demodulation reference signalsare shown; however, the quantity of the demodulation reference signalsdoes not limit the present disclosure and any quantity of demodulationreference signals may be set up according to a system requirement. Itcan be seen from FIG. 6( a) and FIG. 6( b) that the position of thedemodulation reference signal in serving resource block RB 1′ and theposition of the demodulation reference signal in interference resourceblock RB 2′ do not overlap on the temporal frequency resource. In thiscase, serving resource block RB 1′ and interference resource block RB 2′are formed with a plurality of resource elements, respectively, eachresource element occupies a different temporal frequency position (rangeof a specific time and frequency), and are used to transmit a controlsignal, a channel status information reference signal, and ademodulation reference signals and/or data signals, respectively.

In such a situation, serving base station eNB 1 of mobile terminal UE 1can obtain the positions of the demodulation reference signals in theresource block RB 2′ (only one of the demodulation reference signals canbe selected, and although the signal is represented by U, one or aplurality of signals may be possible) by cooperating with base stationeNB 2 of the neighboring cell, and as shown in the resource element(represented by U1) represented by a shaded line in serving resourceblock RB 1′ of FIG. 6( a), performs puncturing at the temporal frequencyposition corresponding to serving resource block RB 1′ transmitted byeNB 1 itself. That is, any signal is prevented from being transmitted inresource element U1 of serving resource block RB 1′.

When mobile terminal UE 1 receives serving resource block RB 1′ fromserving base station eNB 1 and receives interference resource block RB2′ from base station eNB 2 of the neighboring cell by the same temporalfrequency resource (within the range of the same time and frequency),mobile terminal UE 1 can measure the total power of signals at theposition (the same position) of U and U1. Since resource element U1 doesnot transmit any signals, the total power of the measured signal is thepower of the demodulation reference signal transmitted in U. Since abeampattern of the demodulation reference signal of the transmissioncell is identical to a beampattern of a whole of each transmissionsignal of the transmission cell, the power can indicate the interferencepower from neighboring cell eNB 2. Thus, mobile terminal UE 1 can obtainthe interference power from neighboring cell eNB 2. Also, if themeasured interference power from neighboring cell eNB 2 exceeds apredetermined threshold value, mobile terminal UE 1 reports theinterference power to serving cell eNB 1.

FIG. 7( a) and FIG. 7( b) are diagrams showing the set up of theuser-specific reference signal, as a demodulation reference signal,according to another embodiment of the present disclosure, and theuser-specific reference signal can be set up as a new demodulationreference signal other than a specific demodulation reference signal inthe interference resource block. FIG. 7( a) and FIG. 7( b) are basicallythe same as FIG. 6( a) and FIG. 6( b), so the same parts in FIG. 7( a)and FIG. 7( b) as those in FIG. 6( a) and FIG. 6( b) are not describedagain; however, a demodulation reference signal set up newly is furthershown in interference resource block RB 2′ of FIG. 6( b) and indicatedhere by U.

According to the embodiment in the present disclosure, base station eNB2 of the neighboring cell inserts a new demodulation reference signal Uat the positions other than the specific demodulation reference signals,in interference resource block RB 2′. Demodulation reference signal Ualso includes the precoding vector information of the transmissionantenna, similar to the other specific demodulation reference signals ininterference resource block RB 2′. In such a situation, serving basestation eNB 1 of mobile terminal UE 1 can obtain the position ofdemodulation reference signal U inserted in interference resource blockRB 2′ by cooperating with base station eNB 2 of the neighboring cell andperforms puncturing at the same temporal frequency position of servingresource block RB 1′ transmitted by serving base station eNB 1 itself,as shown in the resource element (represented by U1) represented by ashaded lines in serving resource block RB 1′ of FIG. 7( a). That is, anysignal is prevented from being transmitted in resource element U1 ofserving resource block RB 1′.

When mobile terminal UE 1 receives serving resource block RB 1′ fromserving base station eNB 1 and receives interference resource block RB2′ from base station eNB 2 of the neighboring cell by the same temporalfrequency resource (within the range of the same time and frequency),mobile terminal UE 1 can measure the total power of signals at theposition (the same position) of U and U1. Since resource element U1 doesnot transmit the signal, the measured total power of the signals is thepower of demodulation reference signal transmitted in U. Since abeampattern of the demodulation reference signal of the transmissioncell is identical to a beampattern of whole of each transmission signalin the transmission cell, the power can indicate the interference powerfrom neighboring cell eNB 2. This allows mobile terminal UE 1 to obtainthe interference power from neighboring cell eNB 2. Also, if themeasured interference power from neighboring cell eNB 2 exceeds apredetermined threshold value, mobile terminal UE 1 reports theinterference power to serving cell eNB 1.

FIG. 8( a), FIG. 8( b), and FIG. 8( c) are other schematic diagramsshowing inter-cell interference. As shown in FIG. 8( a), the quantity ofexisting neighboring cells is not limited to two, and the quantitythereof may increase to three, for example. Basically, at the time ofreceiving a signal (serving resource block) from serving base stationeNB 1, as shown by a dashed lines in FIG. 8( a), mobile terminal UE 1receives the interference signal (interference resource block) fromneighboring cell eNB 2 and the interference signal (interferenceresource block) from the neighboring cell eNB 3. Mobile terminal UE 1 ofserving cell eNB 1 receives two or more interference resource blocksfrom each of the neighboring cells eNB 2 and eNB 3 on the same temporalfrequency resource, depending on different situations. Since theseinterference resource blocks are positioned on the same temporalfrequency resource, these blocks can be regarded as blocks formed byoverlapping two layers or multilayers, and the total interference poweris equal to the sum of power of the overlapped multilayered interferenceresource blocks. That is, the interference resource blocks that mobileterminal UE 1 of serving cell eNB 1 receives from the neighboring cellseNB 2 and eNB 3 may be multilayered.

The multilayered interference resource block may be generated, not onlywhen the interference signal shown in FIG. 8( a) arrives from differentcells, but also when, as shown in FIG. 8( b), the interference signalsresult from the signals of a plurality of users. In FIG. 8( b), basestation eNB 2 of the neighboring cell includes a plurality of (in thiscase, two) mobile terminals UE 2 and UE 2′, and at the time ofcommunicating with the mobile terminals UE 2 and UE 2′, cell basestation eNB 2 focuses the power of an antenna beam mainly on thedirections of UE 2 and UE 2′. At the time of receiving a signal fromserving base station eNB 1, mobile terminal UE 1 may receive, as shownby a dashed lines in FIG. 8( b), two or more interferences fromneighboring cell eNB 2. The interference from the signal from aplurality of users UE 2 and UE 2′ can be approximated by applying amultilayered interference resource block.

Further, as shown in FIG. 8( c), at the time of receiving a signal fromserving base station eNB 1, mobile terminal UE 1 of serving cell eNB 1may receive a plurality of interferences, as shown by a dashed lines inFIG. 8( c), from neighboring cell eNB 2 and the neighboring cell eNB 3.Since these interference resource blocks are positioned on the sametemporal frequency resource, these blocks can be considered as amultilayered interference resource blocks obtained by overlapping theresource blocks, and the total interference power is equal to the sum ofpower of the overlapped multilayered interference resource blocks. Thatis, the interference resource blocks that mobile terminal UE 1 ofserving cell eNB 1 receives from neighboring cell eNB 2 and/or eNB 3 maybe multilayered.

FIG. 9( a) and FIG. 9( b) are diagrams showing the set up of theuser-specific reference signal, as a demodulation reference signal,according to still another embodiment of the present disclosure. Underan environment shown in FIG. 8( a), FIG. 8( b), and FIG. 8( c), mobileterminal UE 1 receives a serving resource block RB 1″ from serving basestation eNB 1, and at the same time, receives an interference resourceblock RB″ from base station eNB 2 and/or eNB 3 of the neighboring cell.FIG. 9( a) shows serving resource block RB 1″ that mobile terminal UE 1receives from serving cell eNB 1, which is basically the same as servingresource block RB 1′ shown in FIG. 7( a), and the same parts in FIG. 9(a) as those in FIG. 7( a) are not described here again.

FIG. 9( b) shows the overlapped multilayered interference resourceblocks that mobile terminal UE 1 receives from the neighboring cells eNB2 and/or eNB 3 on the same temporal frequency resource (for example,time range from t1 to t2, and frequency range from f1 to f2), i.e., thesame figure shows the sum of first-layer interference resource block RB2,″ and second-layer interference resource block RB 3.″ Both theinterference resource blocks RB 2″ and RB 3″ are basically the same asinterference resource block RB 2′ shown in FIG. 7( b), and the sameparts in FIG. 9( b) as those in FIG. 7( b) are not described here again.A difference is that in the two-layered interference resource blocks RB2″ and RB 3″ shown in FIG. 9( b), a demodulation reference signal infirst-layer interference resource block RB 2,″ is represented by L0 andthe demodulation reference signal in second-layer interference resourceblock RB 3,″ is represented by L1. It should be noted that the temporalfrequency positions of the demodulation reference signals in servingresource block RB 1,″ first-layer interference resource block RB 2,″ andsecond-layer interference resource block RB 3,″ do not overlap eachother.

In such a situation, serving base station eNB 1 of mobile terminal UE 1can obtain the respective temporal frequency positions of thedemodulation reference signals in interference resource blocks RB 2″ andRB 3″ by cooperating with base station eNB 2 and/or eNB 3 of theneighboring cell, and performs puncturing at the respective sametemporal frequency positions of serving resource block RB 1″ transmittedby base station eNB 1 itself of the serving cell. Specifically, theposition of demodulation reference signal as the used demodulationreference signals, at the upper left side of first-layer interferenceresource block RB 2,″ is selected and represented by U, and at the sametime, the position of demodulation reference signal as the same, at theupper left side of second-layer interference resource block RB 3″ isselected and represented by V. Base station eNB 1 of the serving cellperforms puncturing at two positions corresponding to resource block RB1″ transmitted by base station eNB 1 itself, as shown in the resourceelements (each represented by U1 and V1) represented by a shaded line inserving resource block RB 1″ of FIG. 9( a). That is, any signal isprevented from being transmitted in the resource elements U1 and V1 ofserving resource block RB 1.″

Also, since the positions of the demodulation reference signals in eachresource block are orthogonal, base station eNB 2 and/or eNB 3 of theneighboring cell further performs puncturing at the positioncorresponding to the position of the demodulation reference signal inother interference resource blocks RB 3″ and RB 2″ in the two-layeredinterference resource blocks RB 2″ and RB 3,″ at the time oftransmitting the interference resource blocks RB 1″ and RB 2,″ as aresult of which any signal is prevented from being transmitted at thepunctured position. Specifically, in first-layer interference resourceblock RB 2,″ puncturing is performed at the position corresponding tothe position of the demodulation reference signal V of second-layerinterference resource block RB 3″ (for example, represented by V1′) andalso in second-layer interference resource block RB 3,″ puncturing isperformed at the position corresponding to the position of demodulationreference signal U of first-layer interference resource block RB 2″ (forexample, represented by U1′). Thus, the orthogonalization of each ofdemodulation reference signal U in first-layer interference resourceblock RB 2″ and the demodulation reference signal V in second-layerinterference resource block RB 3″ is realized. That is, in theembodiment of the present disclosure, the user-specific reference signal(in this case, the demodulation reference signal) is set up in one layerin the interference resource block of each layer, puncturing isperformed at the same temporal frequency position as the user-specificreference signal in the interference resource block in a layer otherthan this one layer, and any signal is prevented from being transmittedat the punctured position.

When mobile terminal UE 1 receives the serving signal from serving basestation eNB 1 and receives the interference signal from base station eNB2 and/or eNB 3 of the neighboring cell by the same temporal frequencyresource (within the range of the same time and frequency), mobileterminal UE 1 can measure the respective power of signals at thepositions of each resource block U and V. Neither the resource elementsU1 and V1 nor the resource elements U1′ and V1′ transmit a signal, themeasured signal power in the resource element U and the measured signalpower in the resource element V are the interference power of thefirst-layer resource block RB 2″ and the second-layer resource block RB3,″ respectively. Thus, mobile terminal UE 1 can obtain the interferencepower from each neighboring cell eNB 2 and/or eNB 3. Further, if themeasured interference power from neighboring cell eNB 2 and/or eNB 3exceeds a predetermined threshold value, mobile terminal UE 1 reportsthe interference power exceeding the threshold value to serving cell eNB1.

It is possible to prove that “the signal power of interference resourceblock RB” is equal to the sum of “signal power of interference resourceblock RB 2” and “the signal power of interference resource block RB 3”,as below.

As mentioned above, when the interference from the neighboring cells isthe multilayered signal, the reference signals of the different layers,for example, should be orthogonal such as orthogonal with dividing thetime and orthogonal with dividing the frequency. In order to solve theproblem of the power measurement of the multilayered signals, given thattwo-layered interference is transmitted here, the correspondingmathematical model is:{right arrow over (w)} _(data) ={right arrow over (w)} ₁ ·s ₁ +{rightarrow over (w)} ₂ ·s ₂

where, {right arrow over (w)}_(data) indicates entire interference, S₁and S₂ indicate data of the first layer and second layer, respectively,and S₁ and S₂ are independent random variables in the derivationprocess, i.e., the mutual correlations are assumed to be zero. {rightarrow over (w)}₁ and {right arrow over (w)}₂ indicate the precodingvector of the first layer and the precoding vector of the second layer,respectively. Then, in the direction θ, the received interference signalis:S _(data)(θ)={right arrow over (v)} _(θ) ^(H) ·{right arrow over (w)}_(data)

where, S_(data)(θ) is the interference signal received in the directionθ, {right arrow over (v)}_(θ) s a response vector of a matrix in thedirection θ, (.)^(H) indicates conjugate substitution.

Then, power to be received in the direction θ is:

$\begin{matrix}{{P(\theta)} = {E\lbrack {{S_{data}(\theta)} \cdot {S_{data}^{H}(\theta)}} \rbrack}} \\{= {E\lbrack {{\overset{arrow}{v}}_{\theta}^{H} \cdot {\overset{arrow}{w}}_{data} \cdot {\overset{arrow}{w}}_{data}^{H} \cdot {\overset{arrow}{v}}_{\theta}} \rbrack}} \\{= {{\overset{arrow}{v}}_{\theta}^{H} \cdot {E\lbrack {{\overset{arrow}{w}}_{data} \cdot {\overset{arrow}{w}}_{data}^{H}} \rbrack} \cdot {\overset{arrow}{v}}_{\theta}}} \\{= {{\overset{arrow}{v}}_{\theta}^{H} \cdot {E\lbrack {( {{{\overset{arrow}{w}}_{1} \cdot s_{1}} + {{\overset{arrow}{w}}_{2} \cdot s_{2}}} )( {{{\overset{arrow}{w}}_{1} \cdot s_{1}} + {{\overset{arrow}{w}}_{2} \cdot s_{2}}} )^{H}} \rbrack} \cdot {\overset{arrow}{v}}_{\theta}}} \\{= {{{\overset{arrow}{v}}_{\theta}^{H} \cdot {\overset{arrow}{w}}_{1} \cdot {\overset{arrow}{w}}_{1}^{H} \cdot {\overset{arrow}{v}}_{\theta}} + {{\overset{arrow}{v}}_{\theta}^{H} \cdot {\overset{arrow}{w}}_{2} \cdot {\overset{arrow}{w}}_{2}^{H} \cdot {\overset{arrow}{v}}_{\theta}}}} \\{= {{P_{1}(\theta)} + {P_{2}(\theta)}}}\end{matrix}$

where, P₁(θ) and P₂(θ) indicate the power in the direction θ of thesignal of the first layer and the signal of the second layer,respectively.

It can be understood from the above derivation that the solution of thepresent disclosure is correct as it can be seen that the power of themultilayered data in a certain direction (beampattern—can be adjustedcorresponding to the precoding vector of an antenna array by the basestation) is the sum of the power (beampatterns) of the data of eachlayer in that direction. In the demodulation reference signal of a codedivision multiplex, the beampattern is completely different from thebeampattern of the data, it should be noted that the demodulationreference signal cannot be used in the estimation of interference power.

An example of a transmission signal of the demodulation reference signalof the code division multiplex includes:{right arrow over (w)} _(RS) ={right arrow over (w)} ₁·1+{right arrowover (w)} ₂·1

Similar to the above-described calculation of the beampattern of thedata, the following result is obtained:

$\begin{matrix}{{P(\theta)} = {{S_{RS}(\theta)} \cdot {S_{RS}^{H}(\theta)}}} \\{= {{\overset{arrow}{v}}_{\theta}^{H} \cdot {\overset{arrow}{w}}_{RS} \cdot {\overset{arrow}{w}}_{RS}^{H} \cdot {\overset{arrow}{v}}_{\theta}}} \\{= {{\overset{arrow}{v}}_{\theta}^{H} \cdot {\overset{arrow}{w}}_{RS} \cdot {\overset{arrow}{w}}_{RS}^{H} \cdot {\overset{arrow}{v}}_{\theta}}} \\{= {{{\overset{arrow}{v}}_{\theta}^{H} \cdot ( {{\overset{arrow}{w}}_{1} + {\overset{arrow}{w}}_{2}} )}{( {{\overset{arrow}{w}}_{1} + {\overset{arrow}{w}}_{2}} )^{H} \cdot {\overset{arrow}{v}}_{\theta}}}} \\{= {{{\overset{arrow}{v}}_{\theta}^{H} \cdot {\overset{arrow}{w}}_{1} \cdot {\overset{arrow}{w}}_{1}^{H} \cdot {\overset{arrow}{v}}_{\theta}} + {{\overset{arrow}{v}}_{\theta}^{H} \cdot {\overset{arrow}{w}}_{2} \cdot {\overset{arrow}{w}}_{2}^{H} \cdot {\overset{arrow}{v}}_{\theta}} +}} \\{{{\overset{arrow}{v}}_{\theta}^{H} \cdot {\overset{arrow}{w}}_{1} \cdot {\overset{arrow}{w}}_{2}^{H} \cdot {\overset{arrow}{v}}_{\theta}} + {{\overset{arrow}{v}}_{\theta}^{H} \cdot {\overset{arrow}{w}}_{2} \cdot {\overset{arrow}{w}}_{1}^{H} \cdot {\overset{arrow}{v}}_{\theta}}} \\{= {{??}{??}}}\end{matrix}$

From the above calculation, it can be understood that the demodulationreference signal of the code multiplex cannot accurately reflect theinterference power of the data.

FIG. 10 is a diagram illustrating a power sensing reference signalaccording to still another embodiment of the present disclosure.

According to the still another embodiment of the present disclosure, onetype of new user-specific reference signal is designed, and herein, isreferred to as “power sensing reference signal.”

The power sensing reference signal is a reference signal that undergoesthe precoding and is transmitted along with the data that base stationeNB 2 and/or eNB 3 of the neighboring cells transmits to the mobileterminals UE 2, UE 2′ and/or UE 3, and includes information of aprecoding vector of a transmission antenna of the cell. From the above,it can be understood that the demodulation reference signal of a codedivision multiplex cannot accurately reflect the interference power ofthe data, and for a similar reason, this can be applicable to anyuser-specific reference signal, that is, any user-specific referencesignal of a code division multiplex cannot accurately reflect theinterference power of data. From this fact, it can be understood that apredetermined design of the precoding vector must be firstly applied tothe power sensing reference signal so as to realize the estimation ofthe interference power.

As shown in FIG. 10, for example, the power sensing reference signal isset up in the neighboring cells eNB 2 and/or eNB 3 so that thebeampattern of the power sensing reference signal is the sum of thebeampatterns of all the interference signals (multilayeredinterference), received by mobile terminal UE 1 of serving cell eNB 1,from the neighboring cell eNB 2 and/or eNB 3, i.e., is equal to thesuperposition of the beampatterns of the interference signal(interference resource block RB 2″) of first layer and the interferencesignal (interference resource block RB 3″) of the second-layer. That is,in the present disclosure, it is possible to set up the user-specificreference signal as the power sensing reference signal, and at the sametime, to make the beampattern of the power sensing reference signalequal or approximately equal to the superposition of the beampatterns ofall the signals in each interference resource block.

The design of the power sensing reference signal is achieved accordingto one or several types of the following various types of methods:

Method 1: a precoding vector database is searched in the base station(for example, base station eNB 2 and/or eNB 3 of the neighboring cell)that transmits the interference signal, and a precoding vector thatmatches most accurately the summed beampatterns of the transmissionsignal of the interference resource block of each layer is found afterwhich the resultant vector is regarded as the precoding vector of thedesigned power sensing reference signal.

Method 2: a precoding vector of a signal of the interference resourceblock in each layer is set up based on a codebook and the quantity ofavailable precoding matrixes is made finite. In this situation, theprecoding vector of the power sensing reference signal corresponding toa certain precoding matrix can be stored in advance.

Method 3: In addition to the calculation of beampattern of the signal ofeach layer in the interference resource block, the beampattern of eachlayer is overlapped to consider the overlapped chart as the beampatternof the power sensing reference signal, and thereafter, a spectraldecomposition is performed based on the beampattern of the power sensingreference signal to obtain the precoding vector of the power sensingreference signal. The calculation method of Method 3 is as follows: Asshown in FIG. 10, when a two-layered interference resource block isprovided, the precoding vectors of first-layer interference resourceblock RB 2,″ and second-layer interference resource block RB 3,″ areeach known for the base station eNB 2 and/or eNB 3 of the neighboringcell, and therefore, the base station eNB 2 and/or eNB 3 of theneighboring cell performs a fast Fourier transform on the precodingvectors of the interference resource blocks RB 2″ and RB 3″respectively, after which the respective beampatterns of theinterference resource blocks RB 2″ and RB 3″ are obtained by retrievingan absolute value of the result obtained after the fast Fouriertransform and the respective beampatterns of the interference resourceblocks RB 2″ and RB 3 are overlapped, as a result of which the entireoverlapped beampattern is obtained. Subsequently, the precoding vectorof the power sensing reference signal is obtained by spectraldecomposition of this entire beampattern, and at the same time, thepower sensing reference signal corresponding to the entire beampatternis set up according to base station eNB 2 and/or eNB 3 of theneighboring cell from the obtained precoding vector. The number oflayers of interference resource blocks does not limit the presentdisclosure and the interference resource blocks of this embodiment inthe present disclosure can include any number of layers.

The power sensing reference signal may or may not occupy the temporalfrequency resource of the demodulation reference signal (DM-RS). Inreality, the specific position of the power sensing reference signal isnot important, and it may suffice if the puncturing position and theposition of power sensing reference signal correspond to each other; theimportant point is that the beampattern of the power sensing referencesignal should be equal to or approximately equal to the sum of thebeampatterns of a signal of each layer. In this case, the interferedcell can know the total interference power from the reception power ofthe power sensing reference signal.

FIG. 11( a) and FIG. 11( b) are diagrams illustrating the set up of thepower sensing reference signal to the data signal position, according tothe embodiment of the present disclosure. FIG. 11( a) and FIG. 11( b)are basically the same as FIG. 9( a) and FIG. 9( b), and the same partsin FIG. 11( a) and FIG. 11( b) as those in FIG. 9( a) and FIG. 9( b) arenot described again.

In FIG. 11( b), there is shown a power sensing reference signal that canbe set up in either first-layer interference resource block RB 2″ orsecond-layer interference resource block RB 3,″ and it is assumed hereinthat the power sensing reference signal is set up on second-layerinterference resource block RB 3,″ and is set up in the resource elementof second-layer interference resource block RB 3,″ used for transmittingthe data signal. In the figure, the power sensing reference signal isrepresented by W. Thus, the resource element cannot transmit the datasignal.

In such a situation, base station eNB 1 of serving cell, as shown in theresource element (represented by W1) represented by a shaded lines inserving resource block RB 1″ of FIG. 11( a), performs puncturing at theposition corresponding to power sensing reference signal W in resourceblock RB 1″ transmitted by base station eNB 1 itself. That is, anysignal is prevented from being transmitted in resource element W1 ofserving resource block RB 1.″ Further, because of the orthogonalarrangement at the position of the power sensing reference signals ineach resource block, when interference resource blocks RB 2″ and RB 3″are transmitted, base station eNB 2 and/or eNB 3 of the neighboring cellfurther performs puncturing (not shown) at position W1′ corresponding tothe position of the power sensing reference signal of the second-layerinterference resource block RB 3,″ in first-layer interference resourceblock RB 2,″ as a result of which any signal is prevented from beingtransmitted at the punctured position. Thus, the orthogonalization ofpower sensing reference signal W is achieved in the second-layerinterference resource block RB 3.″ That is, in the embodiment of thepresent disclosure, the power sensing reference signal is set up in onelayer of the multilayered interference resource block, and thepuncturing is performed at the same temporal frequency position as thepower sensing reference signal in the interference resource block in alayer other than the one layer so as to prevent any signal from beingtransmitted.

In the present embodiment, the power sensing reference signal occupiesthe resource element used for the transmission of the data signal, inother words, the power sensing reference signal is set up at thetemporal frequency position of the data signal in the interferenceresource block.

When mobile terminal UE 1 receives the serving signal from serving basestation eNB 1 and uses the same temporal frequency resource so as toreceive the interference signal of a multilayer (for example, twolayers) from base station eNB 2 and/or eNB 3 of the neighboring cell,mobile terminal UE 1 can measure the signal power at the position ofpower sensing reference signal W. The beampattern of power sensingreference signal W is equal to the sum of the respective beampatterns offirst-layer interference resource block RB 2″ and the second-layerinterference resource block RB 3,″ and any signal is prevented frombeing transmitted in resource elements W1 and W1′, and therefore, themeasured signal power is the total interference power of first-layerinterference resource block RB 2″ and the second-layer interferenceresource block RB 3.″ Thus, mobile terminal UE 1 can obtain theinterference power from neighboring cell eNB 2 and/or eNB 3. Also, ifthe measured interference power from neighboring cell eNB 2 and/or eNB 3exceeds a predetermined threshold value, then mobile terminal UE 1reports the interference power exceeding the threshold value to servingcell eNB 1.

FIG. 12( a) and FIG. 12( b) are diagrams illustrating the set up of thepower sensing reference signal at the position of the demodulationreference signal, according to the embodiment of the present disclosure.FIG. 12( a) and FIG. 12( b) are basically the same as FIG. 11( a) andFIG. 11( b), and the same parts in FIG. 12( a) and FIG. 12( b) as thosein FIG. 11( a) and FIG. 11( b) are not described here again.

According to the embodiment of the present disclosure, it is possible toset up the power sensing reference signal at the position of any one ofthe demodulation reference signals of first-layer interference resourceblock RB 2″ and second-layer interference resource block RB 3,″ and inFIG. 12( b), there is shown that the power sensing reference signal isset up at the position of demodulation reference signal of first-layerinterference resource block RB 2,″ which is represented by W. Thus, thedemodulation reference signal is not transmitted at the position.

In such a situation, base station eNB 1 of the serving cell, as shown inthe resource element (represented by W1) represented by a shaded line inserving resource block RB 1″ of FIG. 12( a) performs puncturing at theposition corresponding to power sensing reference signal W in resourceblock RB 1″ transmitted by base station eNB 1 itself. That is, anysignal is prevented from being transmitted in resource element W1 ofserving resource block RB 1.″ Also, because of the orthogonalarrangement at the position of the power sensing reference signal ineach resource block, at the time of transmitting interference resourceblocks RB 2″ and RB 3,″ base stations eNB 2 and/or eNB 3 of theneighboring cell performs further puncturing (not shown) at position W1′corresponding to the position of the power sensing reference signal offirst-layer interference resource block RB 2″ in second-layerinterference resource block RB 3,″ and as a result of which any signalis prevented from being transmitted at the punctured position. Thus, theorthogonalization of power sensing reference signal W can be achieved infirst-layer interference resource block RB 2.″ That is, in theembodiment of the present disclosure, the power sensing reference signalis set up in one layer of the multilayered interference resource block,and the puncturing is performed at the same temporal frequency positionas the power sensing reference signal in the interference resource blockin a layer other than the one layer so as to prevent any signal frombeing transmitted.

In this embodiment, the power sensing reference signal occupies theresource element for the transmission of the demodulation referencesignal, in other words, the power sensing reference signal is set up atthe temporal frequency position of the demodulation reference signal inthe interference resource block, by which it is possible to save thetemporal frequency resources of the data transmission.

When mobile terminal UE 1 receives the serving signal from serving basestation eNB 1 and receives the interference signal with multilayer (forexample, two layers) from base station eNB 2 and/or eNB 3 of theneighboring cell by using the same temporal frequency resource, mobileterminal UE 1 can measure the signal power at the position of powersensing reference signal W. The beampattern of power sensing referencesignal W is equal to the sum of each of the beampatterns of first-layerinterference resource block RB 2″ and second-layer interference resourceblock RB 3,″ and any signal is prevented from being transmitted inresource elements W1 and W1′. As a result, the measured signal power isthe total interference power of first-layer interference resource blockRB 2″ and second-layer interference resource block RB 3.″ Thus, mobileterminal UE 1 can obtain interference power from neighboring cell eNB 2and/or eNB 3. Also, if the measured interference power from neighboringcell eNB 2 and/or eNB 3 exceeds a predetermined threshold value, mobileterminal UE 1 reports the interference power that exceeds thresholdvalue, to serving cell eNB 1.

FIG. 13( a) and FIG. 13( b) are another diagrams illustrating the set upof the power sensing reference signal at the position of thedemodulation reference signal, according to the embodiment of thepresent disclosure. FIG. 13( a) and FIG. 13( b) are basically the sameas FIG. 12( a) and FIG. 12( b), and the same parts in FIG. 13( a) andFIG. 13( b) as those in FIG. 12( a) and FIG. 12( b) are not describedhere again.

According to the embodiment of the present disclosure, the power sensingreference signal can be set up at the position of any one of thedemodulation reference signal of first-layer interference resource blockRB 2″ and second-layer interference resource block RB 3,″ and thedemodulation reference signal of which the position has been occupied isset up at another temporal frequency position of the interferenceresource block. In FIG. 13( b), it is shown that the power sensingreference signal (represented by W) is set up at the position of thedemodulation reference signal of first-layer interference resource blockRB 2,″ and at the same time, the demodulation reference signal(represented by V) of which the position has been occupied is set up atthe temporal frequency position for transmission of the data signal inthe interference resource block.

In such a situation, as shown in the resource element (represented byW1) represented by a shaded line in serving resource block RB 1″ of FIG.13( a), base station eNB 1 of the serving cell performs puncturing atthe position corresponding to power sensing reference signal W inresource block RB 1″ transmitted by base station eNB 1 itself. That is,any signal is prevented from being transmitted in resource element W1 ofserving resource block RB 1.″ Also, because of the orthogonalarrangement at the position of the power sensing reference signal ineach resource block, at the time of transmitting interference resourceblocks RB 2″ and RB 3,″ base station eNB 2 and/or eNB 3 of theneighboring cell further performs puncturing (not shown) at position W1′corresponding to the position of power sensing reference signal W offirst-layer interference resource block RB 2″ in second-layerinterference resource block RB 3,″ as a result of which any signal isprevented from being transmitted at the punctured position. Thus, theorthogonalization of power sensing reference signal W can be achieved infirst-layer interference resource block RB 2.″ That is, in theembodiment of the present disclosure, the power sensing reference signalis set up in one layer of the multilayered interference resource blockand puncturing is performed at the same temporal frequency position asthe power sensing reference signal in the interference resource block ofa layer other than the one layer so as to prevent any signal from beingtransmitted.

In this embodiment, the power sensing reference signal occupies theresource element for transmission of the demodulation reference signaland the demodulation reference signal of which the position has beenoccupied is set up at another temporal frequency position of theinterference resource block, and thus, with respect to thesingle-layered or multilayered interference source, in either of thepresent methods, any overheads of puncturing can be retained or reducedand the accuracy for the channel estimation during demodulation is notlowered.

When mobile terminal UE 1 receives the serving signal from serving basestation eNB 1 and when the multilayered (for example, two layered)interference signal is received from base station eNB 2 and/or eNB 3 ofthe neighboring cell by using the same temporal frequency resource,mobile terminal UE 1 can measure the signal power at the position ofpower sensing reference signal W. The beampattern of power sensingreference signal W is equal to the sum of each of the beampatterns offirst-layer interference resource block RB 2″ and second-layerinterference resource block RB 3″ and since any signal is prevented frombeing transmitted in resource elements W1 and W1′, the measured signalpower is the total interference power of first-layer interferenceresource block RB 2″ and second-layer interference resource block RB 3.″Thus, mobile terminal UE 1 can obtain the interference power fromneighboring cell eNB 2 and/or eNB 3. Also, if the measured interferencepower from neighboring cell eNB 2 and/or eNB 3 exceeds a predeterminedthreshold value, mobile terminal UE 1 reports the interference powerthat exceeds the threshold value to serving cell eNB 1.

According to another embodiment of the present disclosure, the powersensing reference signal is transmitted by occupying the position of aCSI reference signal of either first-layer resource block RB 2″ andsecond-layer resource block RB 3″ in two-layered resource block RB″(equal to RB 2″+RB 3″) as the interference, and the puncturing can beperformed at the corresponding position of serving resource block RB 1″which is transmitted to mobile terminal UE 1 by serving cell eNB 1. Atthe same time, the puncturing is also performed at the correspondingposition of the interference resource block in another layercorresponding to the interference resource block of which the CSIreference signal is occupied, in other words, the CSI reference signalsare orthogonal. That is, the power sensing reference signal is set up inone layer of the multilayered interference resource block, and bypuncturing at the same temporal frequency position as the power sensingreference signal in the resource block in a layer other than the onelayer so as to prevent any signal from being transmitted. Here, thepower sensing reference signal occupies the position for transmittingchannel status information reference signal, in other words, the powersensing reference signal is set up at the temporal frequency position ofthe channel status information reference signal in the interferenceresource block, and in this way, the temporal frequency resources of thedata transmission can be further saved. In this method, the overheadresulting from the puncturing can be reduced and the demodulationaccuracy in the neighboring cell is not affected.

According to still another embodiment of the present disclosure, intwo-layered resource blocks RB 2″ and RB 3″ as an interference source,the power sensing reference signal is transmitted by occupying theposition in the control zone of interference resource block RB 2″ or RB3″ in a certain layer, and the puncturing is performed at thecorresponding position of serving resource block RB 1″ transmitted tomobile terminal UE 1 by serving cell eNB 1, and the puncturing can alsobe performed at the corresponding position of the interference resourceblock in a layer corresponding to the interference resource block ofwhich the position has been occupied. In other words, the power sensingreference signal is set up in one layer in the multilayered interferenceresource block, and the puncturing is performed at the same temporalfrequency position as the power sensing reference signal in the resourceblock in another layer other than the one layer so as to prevent anysignal from being transmitted. No data is transmitted in the resourceelement punctured in each resource block. Here, the power sensingreference signal occupies the position in the control zone, in otherwords, the position of the power sensing reference signal is set up inthe control zone of the interference resource block, and in this method,it is possible to reduce the overheads caused by the puncturing and itis possible not to affect the demodulation accuracy in the neighboringcell and not to reduce the accuracy of the channel estimation of theneighboring cell. However, this position can be used only when theavailable resource elements are still present in the control zone.

FIG. 14 is a diagram illustrating the set up of the power sensingreference signal according to another embodiment of the presentdisclosure. In interference resource block RB″ shown in FIG. 14, a4-layered interference resource block is shown, the demodulationreference signals of the interference resource block of each layer arerepresented by L0, L1, L2, and L3, respectively, and an Rel-8 RS signalis indicated by a resource element represented by a slanting line.According to this embodiment, the position of the power sensingreference signal is separated from the Rel-8 RS signal, that is, byseparating the temporal frequency position of the power sensingreference signal and that of the Rel-8 RS reference signal in theinterference resource block of each layer from each other, it ispossible to avoid the adverse effects arising in the course of thesignal reception.

FIG. 15 is a diagram illustrating the set up of the power sensingreference signal when interference arrives from a plurality of terminalsof the neighboring cells. When the interference source is a signal thatthe base station of the neighboring cell transmits to a plurality ofmobile terminals UE, it is probable that the interfered mobile terminalUE 1 occupies a plurality of resource blocks (generally, includingseveral resource blocks continuing in time and frequency), and thus, thedifferent resource blocks of the interfered mobile terminal UE 1 may beinterfered by the signal of the different mobile terminals of theneighboring cell. In this situation, even when each mobile terminal ofthe neighboring cell receives a single-layered signal, it is probablethat the interference from each resource block of the serving cell ismultilayered, i.e., the resource block of each layer may arrive from thesignal of the different mobile terminal in the neighboring cell. In thissituation, the interference from the signals of a plurality of mobileterminals can be approximated using the power sensing reference signal,and the design method therefor is the same as the design of themultilayered interference signal, as shown in FIG. 15.

In FIG. 15, for example, resource blocks RB 1 and RB 1′ are two servingresource blocks continuing in the frequency domain, transmitted by basestation eNB 1 of the serving cell to mobile terminal UE 1. Further,resource blocks RB 2 and RB 3 are two resource blocks continuing in thefrequency domain, transmitted by the base station (e.g., eNB 2) of theneighboring cell to respective different mobile terminals UE 2 and UE 3.The structure of each resource block in FIG. 15 is the same as thepreceding one, and thus, the structure is not described here again. Inthe situation shown in FIG. 15, each of mobile terminals UE 2 and UE 3receives only the single-layered signal, however, mobile terminal UE 1of the serving cell still receives the interference from the signaltransmitted to two mobile terminals UE 2 and UE 3 from neighboring celleNB 2 on a specific temporal frequency resource shown in FIG. 15. Inthis situation, base station eNB 2 of the neighboring cell can set upthe power sensing reference signal only on one part of the resourceblock (e.g., one resource block RB 3), and the beampattern of this powersensing reference signal should be equal to or approximately equal tothe sum of the beampatterns of two-layered resource blocks RB 2 and RB3.

FIG. 16 is a diagram illustrating another example of the set up of thepower sensing reference signal when the interference arrives from aplurality of terminals of the neighboring cell. As shown in FIG. 16, aplurality of resource blocks on the left side are serving resourcesblocks that base station eNB 1 of the serving cell transmits to itsmobile terminal UE 1, the resource blocks represented by a slanting lineon the right side are resource blocks that neighboring cell eNB 2transmits to mobile terminal UE 2 in neighboring cell eNB 2, and theresource blocks represented by a horizontal line on the right side areresource blocks that neighboring cell eNB 2 transmits to mobile terminalUE 3 in neighboring cell eNB 2. In this situation, base station eNB 2 ofthe neighboring cell can set up the power sensing reference signal onlyon one part of the resource block, and the beampattern of the powersensing reference signal should be equal to the sum of the beampatternsof all the resource blocks transmitted to mobile terminals UE 2 and UE3.

FIG. 17 is a diagram illustrating generation of the interferenceresource block when a plurality of mobile terminals exists in theneighboring cell. Given the overhead reduction, it is not necessary toset up the power sensing reference signal in all the interferenceresource blocks. In this situation, one power sensing reference signalshould be set up in several resource blocks separated from each other.One option of the density of the power sensing reference signal is adefinite density in which irrespective of the type of a signal schedulerin the base station and the degree of allocation (neighboring ornon-neighboring) of the resource blocks of the mobile terminal, thedensity of the power sensing reference signal is always uniform. Anotheroption is an adjustable density in which, for example, regarding theallocation of the neighboring resource blocks, the density of the powersensing reference signal is relatively sparse, and on the contrary,regarding the allocation of non-neighboring resource blocks, the densityof the power sensing reference signal is relatively tight. Regarding thesolution in which the density can be adjusted, generally, the adjustmentof density should not be too fast so that the density of a new powersensing reference signal can be notified to the interfered cell.

As shown in FIG. 17, the resource blocks represented by different linesare resource blocks of different mobile terminals, and these resourceblocks are contiguous on time and frequency. In the figure, “◯ (circle)”represents a resource block including the power sensing referencesignal. In this situation, in a plurality of interference resourceblocks contiguous by the temporal frequency, the power sensing referencesignals are set up at fixed temporal frequency intervals.

Further, when there are one or more interference cells, the powersensing reference signal of each cell should have an appropriatemultiplexing mechanism. Based on the multiplexing mechanism of timedivision, frequency division, or code division, the power sensingreference signal can be multiplexed.

FIG. 18 is a diagram illustrating the basic arrangement of a radiocommunication system for realizing the embodiment of this disclosure. Asshown in FIG. 18, the radio communication system of the embodiment ofthe present disclosure includes a serving cell and a neighboring cell,and the serving cell and the neighboring cell include serving basestation eNB 1 and neighboring base station eNB 2. Mobile terminal UE 1of the serving cell receives a serving resource block from serving basestation eNB 1 by using the same temporal frequency resource, and (asshown with a dashed line in the figure) receives an interferenceresource block from neighboring base station eNB 2. The radiocommunication system shown in FIG. 18 further includes puncturing device181 arranged in serving base station eNB 1 and set up device 182arranged in neighboring based station eNB 2. The recitation of servingbase station eNB 1 and neighboring base station eNB 2 is merelyrelative. In mobile terminal UE 2, eNB 2 is the serving base station andeNB 1 is the neighboring base station, and thus, set up device 182 andpuncturing device 181 may be placed in base stations eNB 1 and eNB 2,respectively. In base stations eNB 1 and eNB 2, other than set up device182 and puncturing device 181, for example, a plurality of other meanssuch as a control device capable of controlling the operation of set updevice 182 and puncturing device 181 are further included. These othermeans may suffice to have the same structure as those of the basestation device in the conventional technology, and thus, the detaileddescription thereof is omitted.

According to one embodiment of the present disclosure, set up device 182of base station eNB 2 sets up the user-specific reference signal in theresource block (interference resource block as viewed from UE 1) to betransmitted to mobile terminal UE 2, and the user-specific referencesignal may suffice to be the demodulation reference signal in theresource block or to be the above-described power sensing referencesignal designed solely. Through the communication (in any form that canbe realized by a person skilled in the art) between base stations eNB 1and eNB 2, base station eNB 1 acquires the temporal frequency positionof the user-specific reference signal which is set up in theinterference resource block by base station eNB 2, puncturing device 181in base station eNB 1 performs puncturing at the same temporal frequencyposition as the temporal frequency position at which the user-specificreference signal is set up on the interference resource block, in theserving resource block including the same temporal frequency resource asthe interference resource block, transmitted to mobile terminal UE 1 byserving base station eNB 1 so as to prevent any signal from beingtransmitted at the punctured temporal frequency position.

Mobile terminal UE 1 receives the serving resource block and theinterference resource block by the same temporal frequency resource, andthereafter, measures the power of the set up user-specific referencesignal at the punctured temporal frequency position, as the interferencepower received from base station eNB 2 of the neighboring cell. If themeasured interference power from base station eNB 2 of the neighboringcell exceeds a predetermined threshold value (that can be set upaccording to a system requirement), then mobile terminal UE 1 reports tobase station eNB 1 of the serving cell, i.e., reports the measuredinterference power to base station eNB 1 of the serving cell. If thepower does not exceed it, mobile terminal UE 1 does not report themeasured interference power to base station eNB 1 of the serving cell.

As mentioned above, when the cell where base station eNB 2 exists isconsidered as the serving cell and the cell where base station eNB 1exists is considered as the neighboring cell, in mobile terminal UE 2 inthe serving cell, the set up device arranged in base station eNB 1 andpuncturing device arranged in base station eNB 2 operate according tothe above methods. These are not described here again.

Also, the number of the neighboring cells is not limited to one; anarbitrary number may suffice as long as possible to exist in the system.

FIG. 19 is a flow chart of a method of realizing the embodiment of thisdisclosure.

In step S1901 of the flow chart shown in FIG. 19, the user-specificreference signal is set up in the interference resource block of theneighboring cell. In step S1902 shown in FIG. 19, puncturing isperformed at the same temporal frequency position as the temporalfrequency position at which the user-specific reference signal is set upon the interference resource block, in the serving resource block of theserving cell so as to prevent any signal from being transmitted at thepunctured temporal frequency position. In step S1903, at the puncturedtemporal frequency position, the power of the user-specific referencesignal is measured as the interference power received from theneighboring cell. In step S1904, it is determined whether the measuredinterference power is greater than a predetermined threshold value. Whenthe measured interference power from the neighboring cell exceeds apredetermined threshold value, the process proceeds to step S1905, andin step S1905, the interference power is reported to the serving cell.

The above-described process in step S1901 is realized by, for example,set up device 182 arranged in base station eNB 2 of the neighboringcell, the process in step S1902 is realized by, for example, puncturingdevice 181 arranged in base station eNB 1 of the serving cell, and theprocesses in steps S1903, S1904, and S1905 are realized by mobileterminal UE 1 of the serving cell eNB 1.

This method according to the embodiment of the present disclosure mayfurther include a step of setting up the user-specific reference signalin one layer of the multilayered interference resource block so that anysignal is prevented from being transmitted by performing the puncturingat the same temporal frequency position as the user-specific referencesignal in the interference resource block of a layer other than this onelayer. The method according to the embodiment of the present disclosuremay further include a step of setting up the user-specific referencesignal as the demodulation reference signal in the interference resourceblock. The method according to the embodiment of the present disclosuremay further include a step of setting up the user-specific referencesignal as a new demodulation reference signal other than demodulationreference signal specific in the interference resource block. The methodaccording to the embodiment of the present disclosure may furtherinclude a step of setting up a beampattern of the power sensingreference signal as the sum of the beampatterns of all the signals inthe interference resource block. The method according to the embodimentof the present disclosure may further include a step of setting up thepower sensing reference signal at the temporal frequency position of thedata signal in the interference resource block. The method according tothe embodiment of the present disclosure may further include a step ofsetting up the power sensing reference signal at the temporal frequencyposition of the demodulation reference signal in the interferenceresource block. The method according to the embodiment of the presentdisclosure may further include a step of setting up the demodulationreference signal of which the position is occupied at another temporalfrequency position. The method according to the embodiment of thepresent disclosure may further include a step of setting up the powersensing reference signal at the temporal frequency position of thechannel status information reference signal in the interference resourceblock. The method according to the embodiment of the present disclosuremay further include a step of setting up the position of the powersensing reference signal in the control zone of the interferenceresource block. The method according to the embodiment of the presentdisclosure may further include a step of separating the temporalfrequency positions of the power sensing reference signal and the Rel-8RS reference signal in the interference resource block from each other.The method according to the embodiment of the present disclosure mayfurther include a step of searching a precoding vector database in thebase station of the neighboring cell so as to find a precoding vectorwhich most closely matches the entire beampattern of a signal of eachlayer of the interference resource block so that the resultant vector isregarded as the precoding vector of the power sensing reference signal.The method according to the embodiment of the present disclosure mayfurther include a step of setting up the precoding vector of the signalof each layer based on a codebook and storing beforehand the precodingvector corresponding to the power sensing reference signal. The methodaccording to the embodiment of the present disclosure may furtherinclude a step in which the beampatterns of the signal of each layer inthe interference resource block are calculated, and the beampatterns ofeach layer are overlapped so as to consider the overlapped charts as thebeampattern of the power sensing reference signal, and thereafter,spectral decomposition is performed based on the beampattern of thepower sensing reference signal so as to acquire the precoding vector ofthe power sensing reference signal. The method according to theembodiment of the present disclosure may further include a step ofsetting up the power sensing reference signals at predetermined temporalfrequency intervals, in a plurality of interference resource blockswhere temporal frequencies continue. Each of the above-described stepsmay be realized by, for example, set up device 182 arranged in basestation eNB 2 of the neighboring cell.

According to the adaptive feedback system of the embodiment of thepresent disclosure, uplink feedback overheads can be effectivelyreduced. For example, assuming that each UE is a single receptionantenna and two base stations are each four transmission antennas, thenthe antenna spacing ensures that fading between the antennas is anindependent fading. It is assumed that all the channel informationexists on the base station side and the transmission is a maximum ratiotransmission. In this case, the fact that the adaptive feedback systemcan reduce feedback overhead as shown in the following table is derivedfrom one simple simulation.

TABLE 1 Adaptive-type feedback can effectively reduce feedback overhead.If signal to noise ratio is SIR If signal to noise ratio is >6 dB, donot report SIR >10 dB, do not report 4Tx 41% 56% 8Tx 17% 47%

It is obvious to a person skilled in the art that a method of measuringthe interference power of the neighboring cell can not only be used toreduce feedback overhead of the coordinated beamforming but also beapplied to another communication system to improve the performance ofanother system or to reduce another overhead.

Each of the embodiments in the subject application is merely describedas exemplary, the specific configuration and operation of each of theembodiments do not intend to limit the scope of the present disclosure,a person skilled in the art can generate a new mode of embodiment bycombining a different part or operation in each of the embodiments, andsimilarly, such a possibility matches the idea of the presentdisclosure.

The embodiment of the present disclosure may be realized by hardware,software, firmware, and combination of these methods; however, therealization method shall not limit the scope of the present disclosure.

The mutual connection relationship between each functional element(means) in the embodiment of the present disclosure does not limit thescope of the present disclosure; one or more of these elements mayinclude some functional element or may be connected to some functionalelement.

Above, some embodiments of the present disclosure are shown andexplained in combination with drawings, but, without departing from theprinciples and spirit of the present disclosure, this embodiment can bechanged or modified and still they are within the scope of claims of thepresent disclosure and the scope of their equivalents is obvious to theskilled persons.

The invention claimed is:
 1. A method for mapping a reference signal,the method comprising: mapping a reference signal to at least one firstresource of a plurality of resources in a resource block, the pluralityof resources in the resource block having different time-frequencies;and selecting at least one second resource, on which no signal istransmitted in a cell, from the plurality of resources, wherein, to aterminal in the cell, the mapped reference signal is transmitted on theat least one first resource while no signal is transmitted on theselected at least one second resource.
 2. The method according to claim1, wherein a resource having a time-frequency that is same as atime-frequency of a resource, to which a reference signal is mapped inanother cell, is selected as the at least one second resource.
 3. Themethod according to claim 1, wherein the cell performs a coordinatedtransmission with another cell.
 4. The method according to claim 1,wherein the cell performs a coordinated beamforming with another cell.5. The method according to claim 1, wherein the reference signal is usedfor measuring channel information at the terminal.
 6. The methodaccording to claim 5, wherein the channel information is channel stateinformation (CSI) or precoding matrix index (PMI).
 7. The methodaccording to claim 1, further comprising obtaining channel information,which is measured at the terminal based on the reference signal.
 8. Themethod according to claim 1, further comprising obtaining channelinformation that the terminal measures in the at least one secondresource, on which no signal is transmitted to the terminal in the cell,the channel information being measured based on a reference signaltransmitted in another cell.
 9. The method according to claim 1, whereinthe plurality of resources are comprised of resources used fortransmission of control information and resources used for transmissionof data signal, the reference signal is mapped to at least one resourceof the resources used for transmission of the data signal, and the atleast one second resource, on which no signal is transmitted to theterminal in the cell, is selected from the resources used fortransmission of the data signal.
 10. The method according to claim 1,wherein a Rel-8 reference signal is mapped to at least one resource ofthe plurality of resources, and the reference signal is mapped to aresource different from a resource, to which the Rel-8 reference signalis mapped.
 11. The method according to claim 1, wherein the plurality ofresources include a resource used for transmission of a demodulationreference signal, and the reference signal is mapped to a resource usedfor transmission of the demodulation reference signal.
 12. The methodaccording to claim 1, wherein the plurality of resources include aresource used for transmission of a demodulation reference signal, andthe reference signal is mapped to a resource different from a resourceused for transmission of the demodulation reference signal.
 13. Themethod according to claim 1, wherein the reference signal is mapped in aplurality of resource blocks having a given interval.
 14. The methodaccording to claim 1, wherein the reference signal is a power sensingreference signal.
 15. A base station apparatus configured to perform themethod for mapping a reference signal according to claim
 1. 16. A methodfor measuring channel information, the method comprising: receiving afirst reference signal that is mapped to at least one resource of aplurality of resources in a resource block and that is transmitted in acell, and a second reference signal that is mapped to at least anotherresource of the plurality of resources in the resource block and that istransmitted in another cell, wherein no signal is transmitted in thecell on said at least another resource to which the second referencesignal transmitted in the other cell is mapped, the plurality ofresources in the resource block having different time-frequencies; andmeasuring channel information based on at least one of the first andsecond reference signals.
 17. The method according to claim 16, whereinthe cell is a serving cell.
 18. The method according to claim 16,wherein the cell performs a coordinated transmission with the othercell.
 19. The method according to claim 16, wherein the cell performs acoordinated beamforming with the other cell.
 20. The method according toclaim 16, wherein the channel information is channel state information(CSI) or precoding matrix index (PMI).
 21. The method according to claim16, wherein the plurality of resources are comprised of resources usedfor transmission of control information and resources used fortransmission of data signal, the first reference signal is mapped to atleast one resource of the resources used for transmission of the datasignal, and the second reference signal is mapped to at least oneresource of the resources used for transmission of the data signal. 22.The method according to claim 16, further comprising receiving a Rel-8reference signal mapped to at least one resource of the plurality ofresources, wherein the first reference signal is mapped to a resourcedifferent from a resource, to which the Rel-8 reference signal ismapped.
 23. The method according to claim 16, wherein the plurality ofresources include a resource used for transmission of a demodulationreference signal, and the first reference signal is mapped to a resourceused for transmission of the demodulation reference signal.
 24. Themethod according to claim 16, wherein the plurality of resources includea resource used for transmission of a demodulation reference signal, andthe first reference signal is mapped to a resource different from aresource used for transmission of the demodulation reference signal. 25.The method according to claim 16, wherein the first reference signal ismapped in a plurality of resource blocks having a given interval. 26.The method according to claim 16, wherein the first reference signal isa power sensing reference signal.
 27. A terminal apparatus configured toperform the method for measuring channel information according to claim16.
 28. A base station apparatus comprising: a mapping sectionconfigured to map a reference signal to at least one first resource of aplurality of resources in a resource block, the plurality of resourcesin the resource block having different time-frequencies; and a selectingsection configured to select at least one second resource, on which nosignal is transmitted in a cell, from the plurality of resources,wherein, to a terminal in the cell, the mapped reference signal istransmitted on the at least one first resource while no signal istransmitted on the selected at least one second resource.
 29. The basestation apparatus according to claim 28, wherein said selecting sectionselects a resource having a time-frequency that is same as atime-frequency of a resource, to which a reference signal is mapped inanother cell, as the at least one second resource.
 30. The base stationapparatus according to claim 28, further comprising an obtaining sectionconfigured to obtain channel information, which is measured at theterminal based on the reference signal.
 31. The base station apparatusaccording to claim 30, wherein said obtaining section obtains channelinformation that the terminal measures in the at least one secondresource, on which no signal is transmitted to the terminal in the cell,the channel information being measured based on a reference signaltransmitted in another cell.
 32. The base station apparatus according toclaim 28, wherein said mapping section maps a Rel-8 reference signal toat least one resource of the plurality of resources, and maps thereference signal to a resource different from a resource, to which theRel-8 reference signal is mapped.
 33. A terminal apparatus comprising: areceiving section configured to receive a first reference signal that ismapped to at least one resource of a plurality of resources in aresource block and that is transmitted in a cell, and a second referencesignal that is mapped to at least another resource of the plurality ofresources in the resource block and that is transmitted in another cell,wherein no signal is transmitted in the cell on said at least anotherresource to which the second reference signal transmitted in the othercell is mapped, the plurality of resources in the resource block havingdifferent time-frequencies; and a measurement section configured tomeasure channel information based on at least one of the first andsecond reference signals.
 34. The terminal apparatus according to claim33, wherein said receiving section receives a Rel-8 reference signalmapped to at least one resource of the plurality of resources, andreceives the first reference signal mapped to a resource different froma resource, to which the Rel-8 reference signal is mapped.